The present invention relates to a multiple emulsion having the form of water-phase/oil-phase/water-phase (hereinafter designated as "W/O/W multiple emulsion") which may be used as the fundamental form for various products requiring emulsified dispersion system such as cosmetics, drugs, foods and drinks, etc., and also relates to a process for preparing the multiple emulsion and a cosmetics having the form of the multiple emulsion.
Conventionally, the single emulsions such as oil-in-water type emulsion (hereinafter designated as "O/W emulsion") and water-in-oil type emulsion (hereinafter designated as "W/O emulsion") have been widely utilized as the fundamental form for various chemical products. For example, cosmetics such as creams and lotions mostly use W/O emulsion or O/W emulsion as their fundamental form.
Widely used W/O emulsion type cosmetic creams have the advantages of very smooth appearance, high cleansing effect and excellent emolient effect. They give, however, sticky or oily feelings because their external oil phase are exposed to skin on application. The emulsion stability is reduced if water content exceeds 50 vol % in W/O emulsion. On the other hand, O/W emulsion type cosmetic creams have disadvantages of less cleansing and emolient effects than W/O emulsion type creams although they have the many advantages of excellent extensibility and well refreshing feeling on their application. Since emulsion type lotions are made as a form of O/W emulsion in general, they have not only similar disadvantages as described above, but have often caused the problem of creaming showing unstability.
W/O/W multiple emulsion, which may eliminate both disadvantages of W/O and O/W emulsions, may be utilized as a fundamental form for various products such as cosmetics. The formation of the multiple emulsion, however, unexpectedly occurs during preparation of single type emulsion. There is little reproducibility in preparation of multiple emulsion in addition to extremely low proportion of the multiphase-emulsified particles (the low preparation rate of the multiple emulsion) and extremely poor stability of the multiple emulsion. After all, multiple emulsion is very difficult to be prepared and has not been sufficiently utilized.